Stop Islamization of America (SIOA), created in 2009, promotes a conspiratorial anti-Muslim agenda under the guise of fighting radical Islam. The group seeks to rouse public fears by consistently vilifying the Islamic faith and asserting the existence of an Islamic conspiracy to destroy "American" values. The organization warns of the encroachment of shari'a, or Islamic law, and encourages Muslims to leave what it describes as the "falsity of Islam."

Pamela Geller and Robert Spencer, who took over the group's leadership in April 2010, view SIOA as protecting against a powerful and dangerous "Islamic machine" that stands to threaten the security and cultural fabric of the U.S. Geller, in views she outlines in her blog, has linked Islam to bestiality and rape of minors and described the Qur'an as "inspiring" violence. Geller has also charged that Muslim immigration has caused "rampant" honor killings in North America and Europe, compared Muslims to Nazis and asserted that Hitler was inspired by Islam.

Geller and Spencer work closely with David Yerushalmi, an Arizona attorney with a record of anti-Muslim, anti-immigrant and anti-black bigotry. Yerushalmi is one of the driving forces behind Shari'a-related conspiracy theories and growing efforts to ban or restrict the use of Shari'a law in American courts. Geller and Spencer head the American Freedom Defense Initiative (AFDI), a non-profit organization that was incorporated by Yerushalmi. AFDI and SIOA organize most of their activities and initiatives together, and AFDI serves as host through which Geller and Robert Spencer publish their blogs.

A main focus of SIOA activity has been the proposed Islamic center near Ground Zero. In February 2011, SIOA, together with AFDI, released their film, "The Ground Zero Mosque: Second Wave of the 911 Attacks." The film, directed and produced by Geller, claims to "expose government collusion and media bias," which Geller says "whitewash[es] the links to jihad terror and unsavory financial dealings of mosque organizers…and propagandiz[es] the objectives of America's enemies." For Geller, the film is part of her larger effort to "halt and roll back the advance of Islamic law and Islamic supremacism in America."

Geller has sought to garner public support for her opposition to the proposed Islamic center at various events and rallies. During a June 2010 SIOA demonstration against the proposed center in New York City that attracted thousands, Geller said, "It is unconscionable to build a shrine to the very ideology that inspired the jihadist attacks at ground zero." At a Tea Party convention in Tennessee on May 22, 2010, Geller called the proposed Islamic center "the ultimate flag of conquest."

SIOA also launched an advertising campaign, which ran during the month of August, juxtaposing an image of an airplane headed toward the burning WorldTradeCenter with another building labeled "WTC Mega Mosque" and the words "Why There?"

A month later, SIOA organized what it characterized as a "September 11 Rally of Remembrance" near the proposed center site on the anniversary of the September 11 terrorist attacks. The rally featured a number of politicians, radio personalities as well as 9/11 victims' family members. After a number of commemorative prayers, SIOA head Pamela Geller told rally participants, "Only you can stop this triumpheral mosque on the cherished site of conquered land." Participants carried various banners and signs, including ones that read, "No Obama's Mosque" and "Islam = 1400 years of Aggression, Murder! 'Peace' of Islam = Cutting Non-Muslims to Pieces! Never Submit to Sharia – Islam!"

Dutch politician Geert Wilders, who was introduced by Geller as her "hero," told the crowd: "As we all know, America, New York and shari'a are incompatible…A tolerant society, like your city New York, must defend itself against the powers of darkness, against the forces of hatred, the blight of ignorance….we must never give a free hand to those who want to subjugate us."

In her blog postings and other writings, Geller regularly voices support for Wilders, whom she has described as "the Bravest Man in Europe" and "our proxy in the trial of Western Civilization, protagonist vs Islam, antagonist." She has also indicated that she intends to help garner support for Wilders; she claims to have personally financed Wilder's February 2009 trip to speak at the Conservative Political Action Conference in Washington, DC. A few months later, she served on the host committee of one South Florida event held in Wilders' honor and defended him against criticism related to some of his other scheduled appearances in the area.

SIOA was created to mirror its European "sister" organization, Stop Islamization of Europe (SIOE). Like its American affiliate, SIOE warns of the encroachment of shari'a, or Islamic law. However, SIOE's leaders go one step further, calling for the halt to all mosque construction in Europe.

Geller has also expressed support for the goals and actions of the English Defense League (EDL), a self-described "Counter Jihad movement" based in England. Geller described the group as Europe's "movement for freedom" and promoted EDL events, including a March 2010 rally organized in support of Wilders. In response to an incident in which members of the EDL were implicated in violent clashes with police in the northern English city of Bradford in August 2010, Geller posted the following message to her blog: "The stated goal of the EDL is to oppose militant Islam and the sharia. What's wrong with that? Everything to the PC, leftist slaves in the media and the government." Days later, she defended the group against accusations that it features a neo-Nazi and racist ideology, instead accusing the media of attacking "any and all counter jihad activists."

Anti-Muslim themes can also be seen in Geller and Spencer's impassioned criticism of President Obama, whom Geller has described as "the culmination of the Islamic-leftist alliance." Geller has accused Obama of doing the bidding of "Islamic overlords" and unfairly favoring Muslims, whom she argues have become "a de facto privileged class" in the U.S. Geller and Spencer co-authored the book, The Post-American Presidency: The Obama Administration's War on America, released in July 2010.

SIOA ads have been displayed on public transportation in various cities in the U.S. One set of ads directed viewers to a Web site created by SIOA called "Refuge From Islam." The site claims that Muslim Americans who "long to be free" of their religion are in danger of being killed, and offers "safe houses" for those who want "out." Another set of ads - the "Honor Killing Awareness Campaign" - purports to address young Muslim women feeling threatened by their family for rejecting Muslim values or becoming "too Americanized."

In September 2010, Geller and Florida attorney John Stemberger were sued by Omar Tarazi, a Columbus, Ohio, attorney, for allegedly saying he had contacts with terrorists. Tarazi had represented the parents of Rifqa Bary, a Christian teenager who fled to Florida, saying she feared harm from her Muslim mother and father. In his lawsuit, Tarazi said Geller wrongly linked him to Hamas.